However, such probe relies sensitively to the time evolution of \((\ln {\cal G}_0)^{\prime }\) , which is in general priorly unknown. In order to probe the GW friction, there are two approaches to parametrize the time evolution of \((\ln {\cal G}_0)^{\prime }\) . One is the \(c_M\) -parametrization [1]}, which is based on the evolution of the dark energy in the Universe, and another is the \(\Xi \) -parametrization [2]}, which is theory-based parametrization that can fit a lot of modified gravities.
